Development enhances hypometabolism in northern elephant seal pups ( Mirounga angustirostris)

• Published in: Functional Ecology
• Main Authors: Tift, Michael S., Ranalli, Elizabeth C., Houser, Dorian S., Ortiz, Rudy M., Crocker, Daniel E.
• Other Authors: Costa, Daniel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Elephant Seal; Elephant Seals
• Online Access: http://dx.doi.org/10.1111/1365-2435.12111; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1365-2435.12111; https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.12111

Summary Investigation into the development of oxygen storage capacity in air‐breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater. We describe the developmental patterns of oxygen use during voluntary breath‐holds in northern elephant seals ( Mirounga angustirostris ) at 2 and 7 weeks postweaning. We measured (i) changes in oxygen consumption (VO 2 ) and (ii) changes in venous pH, partial pressure of oxygen ( p O 2 ), haemoglobin saturation (sO 2 ), oxygen content (O 2 ct), partial pressure of carbon dioxide ( p CO 2 ), haematocrit (Hct) and total haemoglobin ( tH b). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath‐hold experiments were conducted in and out of water. Suppression of VO 2 during voluntary breath‐holds increased significantly between 2 and 7 weeks postweaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks postweaning, breath‐hold VO 2 was reduced by 52%. Between the two age classes, this equates to a mean breath‐hold VO 2 reduction of 16% from resting VO 2 . Breath‐hold VO 2 also declined with increasing breath‐hold duration, but there was no direct effect of voluntary submergence on reducing VO 2 . Age did not influence rates of venous p O 2 depletion during breath‐holds. However, voluntary submergence did result in slower p O 2 depletion rates when compared with voluntary terrestrial apnoeas. The differences in whole‐body VO 2 during breath‐holds (measured at recovery) and venous p O 2 (reflective of tissue O 2 ‐use measured during breath‐holds) likely reflect metabolic suppression in hypoxic, vasoconstricted tissues. Consistent p CO 2 values at the end of all voluntary breath‐holds (59·0 ± 0·7 mmH g ) suggest the physiological cue for stimulating ...